DESCRIPTION: The Serum Response Factor (SRF) is likely to function as a regulator of activity-dependent gene expression in neurons. The SRF pathway activates gene expression in response to calcium influx through both L-type voltage sensitive calcium channels (VSCCs) and N-methyl D-aspartate (NMDA) receptor subtypes. In neurons, SRF appears to be a regulator of NMDA receptor-mediated gene expression. Experiments are proposed to elucidate the mechanism by which SRF mediates activity-dependent gene expression, using the c-fos gene as a model system. In the first aim, structure/function analyses of SRF mutants will be used to identify and characterize calcium-responsive domain(s) in response to activation of VSCCs in PC12 cells. In the second aim, c-fos/beta-globin chimeric genes will be used to identify coding region sequence determinants involved in regulating the calcium response and to characterize their mechanism of action. In the third aim, the involvement of SRF in calcium-dependent regulation of c-fos activity will be examined in cultured neurons when NMDA receptors are activated by either synaptic activity or by the neurotransmitter glutamate.